Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Drivetrain rattle

I collected my new toy on Saturday, pictures to follow. I have done 100 miles today and there is a worrying rattle developing from somewhere in the drivetrain. The bevel box is quite quiet the noise is further forward than that, it manifests itself when revs drop below 2000 most noticeably in 4th and 5th.


I assume I should be able to drive around at 30 mph in 4th gear which equates to about 1800 rpm. I have driven a couple of demonstrators but do not remember what the typical speeds in gears were. Could some one tell me what gear you normally use around town at 30 mph. I will call the dealer tomorrow in any case.

Apart from that the car is great, been assaulting the senses all day.

Most likely to be the cush drive (transmission damper) winding itself up. I find that the engine/cush drive combination is not actually as low revving as many might expect - I usually am in third when pottering at 30mph.

And congratulations on the new toy!

Yep, I suspect your revs are just a bit low, surprisingly the engine, or cush drive maybe, likes to be around 2500 - 3000 or above to feel smooth, so try dropping a gear and see if it feels better?

The drivetrain in mine doesn't like anything much below 2000rpm either - shunt, vibration, etc. - so I try to avoid it. Means using 1st gear more than usual but the box is really nice so less of an issue than on most cars.

I've had a few rattles and clonks. Mainly sorted by the dealer but still a few noises that I would rather do without! I also have a slight rattle from the front at idle - this sounds to me like it could be the cush drive but I'm probably wrong.

Probably best - if you can - to trot to your dealer and get them to take a look / listen just in case.

If you read the manual it gives some idications on rev range for the running in period - if I remember the minimum for the first 50 miles is 2700(!) and after that it's 2500. In general 2k rpm is too low for mine, it feels like it will stall.

Mine likes 30 in third, 40 in fourth and you guessed it 50 and above in 5th.

Under 2000rpm in any gear creates massive transmission shunt so I avoid it when ever possible.

Gearbox is as sweet as a nut so no big deal really.

I was talking to an engineering friend of mine of the old school; he looks after the 1916 Dennis fire engine at Imperial College and has an old E type that needs rebuilding, plus a Wankel Norton bike and a big flat BMW-engined bike. He tends to take a negative and opposite view of anything thrown at him, and originally hails from Scotland (these two are not related!).

So it was no surprise that he was very dismissive of big V Twins, telling me that they are inherently out of balance and lumpy, rough running and poor at either end of the rev scale. Maybe he's right! Lucky it's great between 2500rpm and 5000rpm which is plenty for me with that sweet little 'box to stir round.

If an electric version of the 3W is ever launched the thing's going to feel a bit different. Perhaps they'll give it threepenny-bit wheels to replace the vibration?

Has anyone tried using a heavier fluid in the tranny? Using race fluid in my +4 Moss box makes it sound like the M3W does at low revs. I think the noise in the Miata box has to do with the firing pulses of the V-Twin when the Miata box was designed for an I-4 engin.

I would agree with the rev bands suggested - I find anything less than 1800rpm and the transmission train starts to struggle - but just keep revs in the 2000-3500 band and all is well.

I seem to use the box a lot as well - but as has been posted thats a joy anyway.............keep it on the pipes as the two stroke boys would say

Thanks for your responses, it is definitely better at higher revs. My dealer has had a listen and says it is the compensator, (Cush drive ?) and is not overly concerned and says it should get quieter. Time will tell !